From: bbiker <renard@...>
Date: 2006-07-29T11:50:11+09:00
Subject: Re: how to split an array in sub arrays of the same length

bbiker wrote:
> I believe the OP asked how to split an array in "x" sub arrays of equal
> length.
> To me, it appears that the response show how to partition an array into
> sub arrays of "y" elements.
>
> The following method does what the OP asked for, as far as I read it.
>
> class Array
> 	def split(n, b=[], d=[])
> 		#########################################################################
> 		# evenly split array 'a' into 'n' sub arrays
> 		#########################################################################
> 		if self.size == 0 or n <= 0
>     	b = nil
> 		elsif n == 1
>     	b = *self
> 		else
> 			# determine how many elements of the array should go in each sub
> arrays
> 			buckets = n
> 			length = self.size
> 			while buckets > 0
> 				elements = length / buckets + (length % buckets > 0 ? 1 : 0)
> 				d << elements
> 				length -= elements
> 				buckets -= 1
> 			end
> 			# p d
>
> 			# evenly distribute array elements into an array with 'n' sub arrays
> 			start = 0  # start
> 			0.upto(n-1) do |idx|
> 				len = d[idx]
> 				b[idx] = *self.slice(start,len)
> 				start += len
> 			end
> 		end
> 		b
> 	end
> end

Sorry, but I pressed the Post message button too soon.

c =
[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23].split(5)
=>

[[1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, 13, 14, 15], [16, 17, 18,
19], [20, 21, 22, 23]]

Note that the first 3 sub arrays contain 5 elements and the last 2 sub
arrays contain 4 elements.

I am a Ruby newbie and would appreciate a critique on the method I
posted.

Thank You